Examine source code of Remove your watermark

{
  "manifest_version": 2,
  "name": "Remove your watermark",
  "version": "1.0",
  "description": "Hides the static watermark of channels icon in YouTube videos, good to prevent OLED burn-in",
  "icons": {
    "48": "image-48x48.png",
    "128": "NOOOOOOO.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "remove-watermark@example.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}